Cultured mammalian central neurons have been used as a model of the CNS to study the developmental neurobiology of 1) the binding properties of drug and peptide receptors, 2) the functionality of these receptors, 3) opioid peptide synthesis and 4) immunohistochemically identified peptidergic neurons. Receptors sterospecific for opioid peptides are present on both cultured sensory and spinal neurons and increase 20-fold over a four-week developmental period in culture. Receptors sterospecific for the benzodiazepine class of drugs are present on cultured neurons and increase 10-fold over a four week period in culture. Receptors for the excitatory amino acid glutamate-induced influx of 22Na. Cultured neurons can synthesize the opioid peptide methionine-enkephalin from 35S-methionine precursor, after four weeks in culture. Immunohistochemically identifiable neurons containing leucine-enkephalin, methionine enkephalin, substance P or somatostatin are present in culture. The results provide some baseline observations indicating the utility of cultured neurons as an appropriate model system to study biochemically a variety of receptors, as well as mechanisms of peptide synthesis.